The intersection of the Allegheny and Monongahela rivers spawned Pittsburgh which is a city of historical significance for shipping and river transport as well as industries that thrived as a result of this access. You would think that where two of the largest rivers in North America intersect it would create something a bit larger than towns such as Wickliffe, KY and Cairo, IL (no offense to those places). What events, or lack thereof prevented this area from developing into a major American city?